1. Field of the Invention
The present invention pertains to a method of and its apparatus for sandblasting a workpiece which has a surface not to be sandblasted adjacent to a surface to be sandblasted.
2. Prior Art
A chamfering of an end edge Wa of a relatively small workpiece W, such as one shown in FIG. 1, and a peripheral edge Wc of a bore Wb therein, has conventionally been performed by a hand process, utilizing an abrasive tape or the like. However, such method has disadvantages that it is troublesome, time-consuming and inefficient.
As an automated method of such a processing, a sandblasting method may be effected in which abrasive grains comprised of silica sand, alumina, chilled cast iron or the like are caused to strongly impinge against a surface of a workpiece to be processed. However, if the workpiece W has, as shown in FIG. 1, surfaces f.sub.2 requiring a mirror finish adjacent to surfaces f.sub.1 to be processed by the sandblasting, there would be a fear that the abrasive grains impinge also against the surfaces f.sub.2 to exert a bad influence thereupon.